Storing baseline information in EEPROM
Pre-stored no-touch or no-hover (no-event) sensor output values can initially be used when a sensor panel subsystem is first booted up to establish an initial baseline of sensor output values unaffected by fingers or other objects touching or hovering over the sensor panel during boot-up. This initial baseline can then be normalized so that each sensor generates the same output value for a given amount of touch or hover, providing a uniform response across the sensor panel and enabling subsequent touch or hover events to be more easily detected. After the initial normalization process is complete, the pre-stored baseline can be discarded in favor of a newly captured no-event baseline that may be more accurate than the pre-stored baseline due to temperature or other variations.
1. A method for establishing no-event baseline sensor output values for sensors in an event sensor panel without corruption by touch or hover events on or about the sensor panel, comprising:
during boot-up of a sensor panel subsystem,
performing a scan of the sensor panel to obtain new sensor output values,
computing offsets for use in generating normalized baseline sensor output values,
generating the normalized baseline sensor output values,
computing a first value as a function of one or more new sensor output values above the normalized baseline sensor output values,
computing a second value as a function of one or more new sensor output values below the normalized baseline sensor output values,
determining whether the second value is greater than the first value by a predetermined margin,
re-scanning the sensor panel if it is determined that the second value is not greater than the first value by the predetermined margin, and
recapturing the normalized baseline sensor output values if it is determined that the second value is greater than the first value by the predetermined margin.
2. An apparatus for establishing no-event baseline sensor output values for sensors in an event sensor panel without corruption by touch or hover events on or about the sensor panel, comprising:
a panel processor programmed for, during boot-up of a sensor panel subsystem,
performing a scan of the sensor panel to obtain new sensor output values,
computing offsets for use in generating normalized baseline sensor output values,
generating the normalized baseline sensor output values,
computing a first value as a function of one or more new sensor output values above the normalized baseline sensor output values,
computing a second value as a function of one or more new sensor output values below the normalized baseline sensor output values,
determining whether the second value is greater than the first value by a predetermined margin,
re-scanning the sensor panel if it is determined that the second value is not greater than the first value by the predetermined margin, and
recapturing the normalized baseline sensor output values if it is determined that the second value is greater than the first value by the predetermined margin.
3. The apparatus of claim 2 , further comprising:
an event sensor panel; and
one or more event detection and demodulation circuits coupled to the event sensor panel and the panel processor for generating the new sensor output values.
4. A non-transitory computer-readable storage medium comprising program code for establishing no-event baseline sensor output values for sensors in an event sensor panel without corruption by touch or hover events on or about the sensor panel, the program code for causing performance of a method comprising:
during boot-up of a sensor panel subsystem,
performing a scan of the sensor panel to obtain new sensor output values,
computing offsets for use in generating normalized baseline sensor output values,
generating the normalized baseline sensor output values,
computing a first value as a function of one or more new sensor output values above the normalized baseline sensor output values,
computing a second value as a function of one or more new sensor output values below the normalized baseline sensor output values,
determining whether the second value is greater than the first value by a predetermined margin,
re-scanning the sensor panel if it is determined that the second value is not greater than the first value by the predetermined margin, and
recapturing the normalized baseline sensor output values if it is determined that the second value is greater than the first value by the predetermined margin.
5. A non-transitory computer-readable storage medium comprising program code for establishing no-event baseline sensor output values for sensors in an event sensor panel without corruption by touch or hover events on or about the sensor panel, the program code for causing performance of a method comprising:
during boot-up of a sensor panel subsystem,
performing a scan of the sensor panel to obtain new sensor output values,
computing offsets for use in generating normalized baseline sensor output values,
generating the normalized baseline sensor output values for the sensors,
computing a first value as a function of one or more new sensor output values above the normalized baseline sensor output values, and
computing a second value as a function of one or more new sensor output values below the normalized baseline sensor output values;
making a first determination as to whether the second value is less than the baseline sensor output value for any sensor by a first amount; and
recapturing new baseline sensor output values if it is determined that the second value is less than the baseline sensor output value for any sensor by the first amount.
6. The computer-readable medium of claim 5 , wherein the first amount is chosen with sufficient margin to avoid triggering caused by a background noise standard deviation.
7. The computer-readable medium of claim 5 , further comprising:
making a second determination as to whether any positive sensor output value is less than a first threshold, and the first value is less than M times the second number of new sensor output values below the normalized baseline sensor output values, wherein the first value represents a number of new sensor output values above the normalized baseline sensor output values; and
recapturing new baseline sensor output values only if both the first and second determinations are affirmative.
8. The computer-readable medium of claim 7 , wherein the first threshold is a touch threshold.
9. The computer-readable medium of claim 7 , further comprising:
making a third determination as to whether any positive sensor output value has been sustained below a touch threshold for a first time period; and
recapturing new baseline sensor output values if the third determination is affirmative.